To facilitate spinning of a spindle in a spindle seat, a plurality of bearings are sandwiched between a spindle and a spindle seat with each bearing including inner and outer rings respectively abutting against an outer surface of the spindle and an inner surface of the spindle seat. The spindle is usually mounted with a machining device such as a cutlery at a terminating end of the spindle. However, the inner and outer rings of each bearing may displace relative to each other after a period of use due to rotation of the spindle and the weight of the machining device. As a result, the spindle may deviate from an axis about which the spindle is supposed to rotate and be damaged eventually.